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‘ Aug. 13, 1963
c. |_-. SMITH
'
3,100,870
ROOMS FOR TESTING ELECTRONIC EQUIPMENT
Filed May 4, 1959
‘
s Sheets-Sheet 1
O TRANSMITTER
I5
l
T1
CHESTER l_. SMITH
ATTORNEY
Aug. 13, 1963
c. L. SMITH
3,100,870
ROOMS FOR TESTING ELECTRONIC EQUIPMENT
Filed May 4, 1959
3 Sheets-Sheet 2
F
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INVENTOR
CHESTER 1_. SMITH‘
BY
,v rm M ATTORNEY
Aug; 13, 1963
(ILL-SMITH
3,100,870
ROOMS FOR TESTING ELECTRONIC EQUIPMENT
Filed May 4, 1959
5 Sheets-Sheet 3
i
INVENTOR
CHESTER L. SMITH
BY
‘(MM
ATTORNEY
j i United States Patent 0
titans
Patented Aug. 13, 1&63
1
2 .
pair of divergent sections 14 and 15, and the antenna is
mounted at the joint of such sections, substantially mid
way between the ceiling 17 and‘the ?oor 16 of the room
3,19%,87tl
Chester L. Smith, Bedford, Mass, assign‘or to Raytheon
RUQMS FGR 'i‘EdTING ELECTRGNIC EQUWMENT
Company, Lexington, Mass, a corporation of Delaware
Filed May 4, 1959, Ser. No. 819,604
5 Claims. (til. 325-67)
11.
..
As viewed in FIGURE .3, the ceiling 17 is provided
with an inwardly directed offset section 18, including a
pair of planar portions 19/ and '21}. Opposite to the
- This invention relates generally to test rooms for elec
section 18 in the ?oor-.16 is another offset section 21,
tronic equipment and more particularly‘ to microwave
including a pair of planar portions 22 and 23. The pur
darkrooms wherein parasitic re?ections which might other 10 pose of the sections 1% {and 21 will ‘be described later in
Wise-atfect the equipment under test are either eliminated
or are substantially reduced.
The prior art has been concerned with the elimination
of re?ections in such test facilities by the use of wave
this speci?cation.
-
The side walls 24 and 25‘ are of a ‘general toothed or
serrated form between their juncture with sections 14'
and 15 of the forward wall of room 11 and with the
traps, wall coating and certain expensive microwave a-b 15 rear'wall of the room for a purpose to be described. The
sorbent wall coverings. While certain prior art arrange
walls 24 and 25 connect with the rear wall 236 which in—
ments have proven most effective, ‘they do not lend them
'cludes a straight panel 27 normal to the antenna lit and
selves to mobility of use, to adaptability with diverse
a pair of slightly angled panels 218‘ and 29. In wall 24
types of equipment under test, or to practical cost ?gures
from a construction standpoint.
‘
adjacent to panel 23 of the rear wall a double door 3%}
20 is provided as an access opening to the room.
It is therefore the primary object of this invention to
provide an improved and efficient microwave darkroom
which overcomes the disadvantages of the prior art.
A more speci?c object of this invention is to provide a
microwave darkroom wherein any re?ections from the 25
wall surfaces of the room are redirected back toward a
transmitter whereby the receiver in the equipment under
test is not subjected to such re?ections.
Another object of this invention is to provide a micro
wave darkroom of such a geometrical design as to sub
stantially prevent ‘re?ected energy item the room sur
faces from reaching the equipment under test in the
room.
.
‘
‘
Y
‘
A further object of this invention is to provide a micro
wave‘ darkroom wherein the surfaces of :the room be
tween a ‘transmitting antenna and a receiving antenna in
the equipment under test are deformed or arranged in
such a manner that any re?ected energy ‘from the Walls
derived from the side lobes of the transmitting antenna
is redirected to the transmitting antenna.
.
,
Another object of this invention is to ‘provide a micro
waye darkroom of relatively low cost as compared to the
prior art.
i
.
A still further object of this invention is to provide
a microwave darkroom which is of a knockdown character
to render it adaptable to be readily movable to different
test sites.
With the foregoing and other objects in view, the in
The entire enclosure constituting the room 11 is of a
knockdown character to render the unit readily movable
and adaptable to manufacturing and test tacilit-ies. The
basic simple and economic structure throughout consists
of plywood panels 31 secured to two by four framing 32
asris well detailed in FIGURES 4 and 5. The plywood
is secured to ‘the framing as by nails. The individual
panels formed ‘by the framing 32 are secured by bolts
33 to adjacent panels. The size of each panel 34 form—
ing a part of the side walls 24 or 25* as well as the
number of panels and the general geometry of the room 11
is developed from a study ofthe type of antenna pattern
originating at the transmitter antenna Ill and its relation
ship to the ‘receiving antenna 12 in the equipment under
test with the distance between the two antennae being of
prime consideration. The geometrical con?guration of
all the surfaces of the groom is such that any wall panel
such as ‘35 facing thenantenna 10 is situated in a plane sub
stantially normal to the path of any energy received from
40 the antenna. Each such facing panel 35 ‘is. covered with
.a layer of microwave absorbent material 36 of any well’
known or suitable type. The panels 35, by being normal
to the path of the received energy from side lobes of
the antenna pattern, re?ect any energy not absorbed di
rectly back toward the antenna 1d‘ from whence it may be
directed outwardly again to strike a panel 35 on the op
posite wall of the room. By thus containing the side
lobes of the radiant pattern, little or no re?ected energy
vention resides in the following speci?cation and appended ‘
is permitted to reach the environment of the receiving
claims, certain embodiments and details of ‘construction 50 antenna 12. The antenna 12 then receives only that por
being illustrated in the accompanying drawings in which: .
FIGURE -1 is a fragmentary interior‘yielw of the micro
tion of a transmitted signal from ‘antenna 16 which it is
wave darkroom of this invention viewed longitudinally of
to testing. If the re?ected energy were not contained
and were permitted to reach the antenna 12 then a test
run of the ‘equipment 151 might be faulty or meaningless.
the room from a receiver position;
I
FIGURE 2 is a sectioned plan view of the microwave
darkroom of this invention;
supposed to receive to properly subject the equipment 13
The offset sections 18 and 21 in the ceiling and ?oor '
of the room are covered with a layer of microwave ab
along the lines 3—3 of FIGURE 2;
sorbent material 37. The sections 18 and '21 substantially
FIGURE 4 is a fragmentary detail in section of the
prevent any re?ected energy ‘from the floor or ceiling from
60
indented wall joint structure at the point 4 in FIGURE
reaching the antenna 12. Whatever energy is not ab
2; and
.
‘
'
sorbed by the material 37 on panels 2-2 or 23 is reflected
FIGURE 5 is a fragmentary detail in section of the
back toward the antenna 10 or away from general area
protruding wall joint structure at the point 5‘ in FIG-.
of antenna 12. Thus a portion of a minor lobe of a
FIGURE 3 is a sectioned view in side elevation taken
‘
URE 2.
‘
‘
‘ Referring more particularly to the ‘drawings, it will be
noted that a transmitting antenna. 11) is mounted on the
pattern radiating from antena 10‘ might strike the sur
3 face of panel 22. The angle of incidence of this energy
may send the re?ected portionof the energy rearwardly
and above the antenna 12, according to design. Upon
forward wall of the darkroom generally indicated at 11.
The antenna 1% is connected to suitable generating equip
‘ striking the rear panel 27 or 29, which is covered with
ment (not shown) to transmit energy of a certain pat
microwave absorbent material 38, more of the energy is
70
tern to the receiving antenna 12 contained within equip
absorbed. Any re?ected portion of the remaining energy
ment 13' under test illustrated in box form within the
will be redirected forwardly of the room andpast the
room. The wall supporting the antenna 10* includes a
equipment 13 where it will ‘be further- dissipated by the"
3,100,870
.
wall coverings on the angled, covered surfaces in the
forward part of the room.
7
With this construction it is not necessary to cover the
panels 34 of the toothed side walls 24 and 25‘ with ab
A,
tive to the transmitting antenna as to re?ect any energy
received from the transmitting antenna away from the
receiving antenna and toward another room surface lo
cated on a different wall.
sorbent "material, thereby reducing the cost of constrnction
considerably over prior art rooms wherein the entire
2. The invention according to claim 1 wherein said
reflecting room surfaces are covered with microwave aba
interiors were covered. Likewise it is not necessary to
cover the ceilingor ?oor of the room 11 rearwardly of
sorbent material.
the room is such as to direct any unwanted re?ected en
of toothed form over theirylength with-each toothed por- -
I
_
3. A microwave darkroom for testing electronic equip
ment by the transmission of radiant energy between trans
the receiving antenna.
,
It should therefore be apparent to one skilled in the 10 mitting and receiving antennae spaced apart in’ said room
which comprises a pair of side Walls, said side walls being
art that the geometrical ‘design of all of the surfaces‘ of
tion thereof having a ?at panel mounted in a plane normal
to the propagation axis of energy received from the trans
' the structure provides that certain of the wall surfaces 15 mitting antenna, a ceiling for the room, a floor for the
room, said ceiling and ?oor'including facing, inwardly
arecovered with absorbent material so that the energy
offset sections located at a predetermined position inter
' level of any re?ected portion of a wave is decreased with
mediate the sp-acing between the transmitting and receiv
each re?ection until complete dissipation is achieved. Thus
ing antennae, a :front wall having rearwardly diverging
theinvention does not rely solely on the material used
for absorbing microwave energy, or upon complex de 20 panels joining with the side walls, and a rear wall con»
znected with said side walls to complete the enclosure, the
signs or arrangements of such material, but merely on’
geometry of said walls and panels being so calculated
?at panels of ‘such material with partial re?ections in di
relative to the position of the transmitting antenna as to
rections away from the receiving antenna 12 on the equip
re?ect any energy received from the transmitting antenna
ment 13 under test,
'
'
V
The exact geometrical design of the room is calculated 25 away from the environment of the receiving antenna and
toward another room surface.
.
l
in accord with the type of antenna‘ used for transmitting
4. The invention according to claim 3 wherein said re
and receiving, the equipment under test and the required
ilecting panels and Walls are covered with microwave
spacing between these elements to achieve a proper test.
absorbent material.
,
It will be obvious to oneskilled in the art therefore that
5. The invention according to claim 3 wherein portions
the character of the room as to shapes, sizes and details 30
of the ceiling and ?oor including the offset sections, the
of construction may vary under certain conditions and
ergy originating at the antenna 10 away from the receiv
ingantenna 12. In addition to the geometrical features
requirements, all suchvariations being well within the
purview of this invention and the appended claims.
I claim:
'
1. A microwave darkroom for testing electronic equip
ment by the , transmission of radiant energy between
normally positioned panels of the side walls, and the
.front and rear walls of the room are covered with micro
wave absorbent material.
References Cited in the ?le of this patent V
transmitting and receiving antennae spaced apart in said
room which comprises, a pair of toothed side wall sur
UNITED STATES’ PATENTS
2,594,971’
‘ Moullin _________ _;____ Apr. 29,‘ 1952
faces spaced :equally to either side of a line between ' ' 2,599,944
- the transmitting and receiving antenna, ceiling and ?oor 40 2,656,535
Neher ______________ _._.__ Oct. 20, 1953
2,870,439
Stinehelfer _____ .__' _____ -f- I an. 20, 1959
surfaces having spaced, facing inwardly, offset sections
,7 ‘located at a predetermined position intermediate the spac
- ing between the transmitting and receiving antennae, and
‘ ‘front and rearwall surfaces for said room, all said room
de?ning surfaces being so geometrically arranged rela
Salisbury _____ __' _____ _._ June 10, 1952. r
OTHER REFERENCES
.
,“Design and ‘Build an Anechoic Chamber,” Electronic
:Ind‘u‘stries',‘April 1959, pp. 72-76.
p
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